and I am asking what makes them "a good thing in the flavour department"? In other words, I interpret your statement above -- and please correct me if I have misunderstood -- as saying that a 55mm group tastes not only different from the standard 58mm group, but somehow better. I am asking what the flavo(u)r difference is. Does it taste sweeter? Deeper? Richer? Is it more complex, with more layers, and a longer finish? In what ways does the 55mm diameter affect the taste, that a 56, 57, or 58mm diameter does not?

I believe you that the 58mm standard is rather arbitrary, and you may be correct: there is nothing more than tradition and/or laziness that maintains the 58mm standard.

beanflying Said:

Della Corte and GS3's are some current examples of 53 or 55mm PF's I think and are some of the best machines in the world.

I was under the impression that Dalla Corte employs 54mm groups and that La Marzocco uses 57mm groups in all of their machines, including the GS/3.

Furthermore, I believe there must be a reason as to why Dalla Corte, for example, chose to employ a 54mm group, or La Spaziale uses a 53mm group. And certainly logic suggests that smaller/deeper would (should) somehow lead to a different extraction than wider/shallower. But no one has ever been able to quantify for me what that difference is in the cup, where it counts! I can see where a 6.89% size reduction (54mm, down from 58mm) MIGHT make a difference . . . kinda, sorta. But downsizing from 58mm to 57mm is a reduction of 1.72%, and that is far too small IMHO to make any difference whatsoever.

apologies I was trying to avoid further hijacking than necessary as it's a big subject and worthy of its own book ;-) . The initial point was seriously broaden up your options and consider the 55mm grouped machines.

Everything I have seen of the Arduino leaves me to believe it shares the same groups as my Fioranzato and as stated earlier the Izzo is better.

It's a shame that levers are not more in use so you can go have a play before you buy.

The size of a lever group is only one of many factors in the machine design which influence the flavour of the coffee extracted from it.

Factors such as Boiler shape and size. Diameter, thickness and length of tubing used.Whether a machine uses a Dipper or HX system.The actual internal and external design of the group head.Even something as simple as changing the group to boiler gasket material can make a difference.etc

I cannot see how it is possible to determine that a 53mm group head is better than a 58mm one without being able to swap the heads from machine to machine.Even if you were to make up adaptor plates to enable you to swap heads, the plates themselves would have some effect on the brewing process.Without the ability to swap, the only valid conclusion you can come to is that one machine ( to your palate ) produces a better coffee.

Coffee machines are generally designed ( IMHO) as a complete system and should be evaluated that way.

As a lot of the current breed of lever machines share groups and similar if not the same boilers from a common source manufacturer (several of them are identical internally) it is relevant to compare the groups as being similar if not the same in the results you are likely to achieve. The only other way is to try and get a go on them rather than speculation from the outside without first hand knowledge.

Older machines built by each factory I would agree totally that you can't compare one with the other and discussion of an individual machine being this way or that in flavour or results but that's well OT.

FWIW, Joat, I have never seen (that I can recall) anyone ever saying that a 58mm is REQUIRED when making recommendations. OTOH, I have seen people insist on -- for example -- an e61 group . . . that is a different "requirement" -- coincidentally a 58mm -- and equally unnecessary. (Usually the one insisting is the OP, saying "I want a machine that has this and that and an e61 group . . . ")

All I am trying to discover is WHAT TASTE DIFFERENCES there are between X and Y, when X = 58mm and Y = 55. Tim said "The 55mm groups are a good thing in the flavour department . . ." and I'm just trying to discover what makes it so. When someone makes a statement like that, I don't think it's too much to ask "why." Time may very well be right. Or not. And no one is saying, "Give me 58mm or give me Folger's!" ;^)

I know how, for example, aging a Cabernet Sauvignon, a Pinot Noir, a Syrah, or other wine will change if the oak barrel is new or used once, twice, three times before; if it is Tronšais, Allier, Sa˘ne, Limousin, Nevers, Appalachian, Wisconson, or Oregon oak; if it is 225L in capacity, 600L, or 3000L, or something larger; if the oak isn't oak at al, but rather chestnut, redwood, or . . . but what I don't understand is how a shot is affected by a 55mm group versus a 58mm group.

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